Field of the Invention
The present invention relates to a powertrain used for a hybrid vehicle.
Description of Related Art
Since a hybrid vehicle, which is a vehicle driven by a combination of electrical power and a power source of an internal combustion engine, is controlled so as to be operated at a point of high efficiency of a system by an engine and an electrical motor to thereby efficiently reduce exhaust gas while having excellent efficiency, it has been implemented as alternative of an environment-friendly vehicle.
A power branch method of the above-mentioned hybrid vehicle includes a mechanical flow in which power of the engine is directly transferred to an output shaft using a power branch apparatus that branches a power flow such as planetary gear set and an electrical flow in which a generator is driven using the power of the engine and a battery is charged with the generated power or a motor is driven by energy of the charged battery.
The power branch type of a hybrid system as described above has advantages that the engine is able to be operated independently from the output shaft, the engine may be freely turned on/off during the driving, and it is possible to implement an electrical vehicle mode.
In addition, since the power branch type of the hybrid system has advantages that the engine may be efficiently driven by an electrically variable transmission (EVT) effect due to two motor generators and the motor has a constant output in response to speed, it does not basically require a transmission.
However, in order to keep the highest speed of the vehicle to be high and secure low speed torque, the transmission is required.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.